The present invention relates to a unit for preparing groups of products in layers for palletizing, in particular, but without limiting the scope of the invention, groups of roll products for bathroom and/or household use.
It is well known that downstream of machines which produce packs of roll products, in various configurations to form loose groups or groups which are grouped together and overwrapped to form bags, there are palletizing islands for the loose groups or bags.
The palletizing island is fed by a belt connecting it to the production machines. The belt feeds batches of loose products or bags (obtained from a bagging unit upstream of the palletizing island) one after the other.
The groups or bags are positioned in a first substation of the palletizing island, from where a suitable first unit forms a layer consisting of a predetermined number of groups of products or bags, according to parameters preset by the logic system which controls the palletizing island.
The layer formed in this way is usually fed until it is close to a second substation having a second logic unit (a robotic unit) with movable grippers for picking up the entire layer of products prepared and moving it to a pallet positioned at a predetermined point of the palletizing island.
The pallet complete with two or more stacked layers of bags or groups of loose products is sent to warehouses (which may or may not belong to the manufacturer) which subsequently ship the pallets.
As already indicated, the palletizing island has a microprocessor control system designed to program and optimize the product layering geometry according to the data entered, that is to say, the type of product to be layered (bag or loose batch and relative dimensions) and the dimensions of the pallet to be used.
With suitable algorithms or direct commands from the operator, the system allows programming of the optimum arrangement of the products on the receiving surface to form the layer (and subsequent layers, which may differ from one another in terms of the relative arrangement of the groups of products) and in such a way as to optimize the movements of the robotic product pick and place unit.
Therefore, once programmed, said system controls the movement of the two robotic units operating in the palletizing island.
At present, three different types of units may be used for layering.
The first has a series of infeed channels for the groups or bags of products arriving and a plurality of stops, “blockers”, devices for checking movement and pushers acting on them, which can be switched on and off on a relative layer preparation surface or belt.
These elements are moved according to a series of sequences programmed by the control logic unit so as to arrange the groups or bags according to a predetermined pattern to form the layer.
The second type of layering unit is provided directly by the above mentioned robotic unit which immediately picks up the products arriving from the first belt and creates the layer directly on the pallet. Said solution is possible if the machines upstream of the palletizing island have low production rates.
The third type of solution (of particular interest in this text) consists of a robotic device with Cartesian axes (also known as a “pick and place” unit to experts in the field), comprising a gantry frame positioned over the first feed belt and a second belt, parallel with the first, on which the products are placed to form the layer, which is then fed towards the second robotic unit for palletizing.
The frame has a set of elevated guides to allow an element for picking up/releasing the groups or bags to move according to four axes (parallel with the belts—X—, transversal to the belts—Y—, vertical—Z—and at an angle—α—for product rotation) driven by relative drive units.
Therefore, the pick up/release element is controlled by the logic unit and, depending on layer forming parameters, moves between the first belt, to pick up the products, and the second belt to release the products in a predetermined position and according to a cyclical sequence with movement along and around the four axes.
The latter solution, widely used to prepare layers of products, allows good product layering in the unit of time, but has a rather heavy and relatively expensive structure, since it needs two crossed guides able to move with the pick up and release element, vertical guides, and a system for rotation of said element to perform all of the movements necessary.
In addition to this, a drive unit is required for each type of axial movement, associated with the pick up and release element and able to move with it, together with the kinematic connecting systems.